Automatic transmissions, especially for motor vehicles, include, in accord with the state of the technology of planetary gearsets and which are shifted by friction based shifting elements, such as clutches and brakes are customarily connected with a start-up element, which is augmented by a bypass clutch, which may be, for example, a hydrodynamically powered torque converter or a fluid clutch.
Within the framework of DE 101 15 983 A1 of the applicant, for example, a multi-speed transmission is described, having an input shaft which is bound to an input-sided gear set, and an output shaft, which is connected with an output-sided gear set, and has a maximum of seven shifting elements, the selective shifting of which, effectively shifts at least seven forward gears (without range shifting). The input-sided gear set is composed of a shiftable or a non-shiftable planetary gearset or, alternately, can be composed of two non-shiftable, mutually coupled planetary gearsets. The output-sided gear set is designed as a two carrier, four shaft transmission with two shiftable planetary gearsets and four free shafts. The first free shaft of this two-carrier, four shaft transmission is bound to the first shifting element, the second free shaft is connected to both the second and third shifting elements, the third free shaft engages the fourth and fifth shifting element and finally, the fourth free shaft is bound to the output shaft. In the case of a multi-speed transmission with a total of six shifting elements, in accord with the invention, the proposal can be made, to the effect that the third free shaft or the first free shaft can be bound additionally with a sixth shifting element. In the case of a multi-speed transmission with a total of seven shifting elements, in accord with the invention, the proposal can be made, that the third free shaft be bound additionally to a sixth shifting element and the first free shaft be additionally connected to a seventh shifting element.
A plurality of other multi-speed transmissions are, for example, also disengaged by DE 101 15 995 A1 of the applicant, wherein four shiftable, mutually coupled planetary gearsets and six or seven frictional shifting elements are provided, by the selective engagements of which, a speed of rotation of the input shaft of the transmission is to be transmitted to an output shaft of the same, so that nine or eleven forward gear stages and at least one reverse gear stage can be implemented. In accord with the therewith accompanying transmission diagram, in each gear two of three shifting elements are engaged, whereupon, a change from one gear to an immediately next higher successive gear, or to an immediately next lower gear, in order to avoid range shifting, respectively only one engaged shifting element need be disengaged and a previously disengaged shifting element can be disengaged.
Further in the generic, unpublished patent application DE 10 2005 0023 37.1 of the applicant, a multi-speed transmission is proposed with one input shaft, one output shaft, four mutually coupled single planetary gearsets and five shifting elements, whereby eight forward gear can be employed, these being free from range shifting, and shifted into in such a manner, that during one gear change from a forward gear into the next successive higher or lower forward gear, only one of the previously engaged shifting elements need be disengaged and only one of the previously disengaged shifting elements need be engaged. This known multi-speed transmission also possesses a reverse gear. In all forward gears as well as in the reverse gear, three shifting elements are engaged. Relative to the kinematical coupling of the four planetary gearsets among each other as well as to the shafts for input and output, provision has been made to the effect that: a carrier of the fourth planetary gearset is connected to the input shaft to form a first shaft of the transmission, a carrier of the third planetary gearset and the output shaft are bound together to form a second shaft of the transmission, a sun gear of the first planetary gearset and a sun gear of the fourth planetary gearset are connected together to form a third shaft of the transmission, an ring gear of the first planetary gearset forms a fourth shaft of the transmission, an ring gear of the second planetary gearset and a sun gear of the third planetary gearset are bound together to form a fifth shaft of the transmission, a carrier of the first planetary gearset and an ring gear of the third planetary gearset are bound together, to form a sixth shaft of the transmission, a sun gear of the second planetary gearset and an ring gear of the fourth planetary gearset are bound together to form a seventh shaft of the transmission and, finally, a carrier of the second planetary gearset forms an eighth shaft of the transmission. Relative to the kinematical coupling of the five shifting elements to the four planetary gearsets and to the shafts for input and output, provision has been made to the effect that: the first shifting element can be placed in the direction of the power-flow between the third shaft and the housing of the transmission, the second shifting element can be placed between the fourth shaft and the housing of the transmission, the third shifting element can be placed between the first and the fifth shafts, the fourth shifting element can be placed either between the eighth and the second shafts, or between the seventh and fifth shafts, or between the seventh and eighth shafts or between the fifth and eighth shafts.
Automatically shiftable vehicle transmissions, which are based on planetary gear arrangements, are generally of the currently accepted state of the technology, and consequently the subject of frequent descriptions and are subject to continual development and improvement. Accordingly, these transmissions should possess a sufficient number of forward gear stages as well as at least one reverse gear stage. Advantageously, these known transmissions should also have a very satisfactory ratio with a high degree of spread, as well as favorable steps between the gears. In addition, these transmissions enable a high startup and acceleration ratio in a forward gear and a have a direct gear for use in both passenger vehicles and trucks. Beyond this, these transmissions should be manufactured with small cost and little effort and require a minimal number of shifting elements and, where sequential shifting is required, should avoid double shifting, so that for shifting in defined gear-groups respectively, only one shifting element need be changed.